1. Field of the Invention
The present invention relates to a disk brake having a plurality of pistons disposed side-by-side for pressing a pad.
2. Description of the Prior Art
A disk brake having a plurality of pistons has advantages in that the diameter of each piston can be made smaller than in a case where a single piston is used, and it is therefore possible to apply a braking force to the disk at a position as remote from the axle as possible, and that such a braking force can be distributed by a plurality of pistons, and further that it is advantageous in achieving a reduction in size. Accordingly, this type of disk brake is widely applied to two-wheeled vehicles.
A plurality of cylinders for receiving these pistons need to communicate with each other in order that the same fluid pressure can be applied to the plurality of pistons simultaneously. Hitherto, communication between the cylinders has been provided by a hole that that extends obliquely from the bottom of one of each pair of adjacent cylinders toward the other cylinder, and another hole extends obliquely from the bottom of the second cylinder toward the first cylinder so that these two holes intersect each other, as will be described later in detail with reference to the drawing. Accordingly, two holes need to be machined to obtain one communicating portion. Thus, the prior art requires a large number of steps for machining process and hence, costs a great deal.
When the number of cylinders is three or more, some of the axes of the holes intersect each other at the cylinder opening side. Accordingly, drill driving units for machining such holes interfere with each other, so that it is impossible to make a boring device that machines a plurality of holes in one stroke. This is another factor that necessitates a large number of machining steps.